Simplex data communication systems, also known as one-way or passive systems, are employed in connection with paging. Generally speaking, one or more transmitters broadcast data communications. The communications include data which identify specific pagers. A population of pagers receives the broadcast communications. When one of the population of pagers identifies a communication directed to it, it alerts a subscriber to the incoming communication and often displays a numeric or alphanumeric message carried by the communication. However, due to the simplex nature of the communications, the system does not know when a pager fails to receive a page directed to it.
Conventional paging systems experience a problem related to a limited range. A paging system works only when its pagers reside within the area covered by the system's transmitters. When subscribers travel outside this area, their pagers cannot receive calls. This problem is exacerbated by the simplex nature of the communications which prevents the system or the sender of the page from knowing whether the page was actually received by the target pager.
A related problem is that of limited information transmission capacity for delivering pages. As any single area of coverage increases to better serve subscriber needs, the population of pagers covered by the area likewise increases. As the population of pagers increases, the number of data communications increases. Thus, as a coverage area increases, a point of diminishing returns is reached. The number of data communications is so great that an unacceptable delay in the delivery of pages is experienced.
The limited range and limited capacity problems are addressed, at least in part, by the use of a paging system with multiple transmitters distributed throughout a wide area of coverage. The multiple transmitters distributed throughout a wide area extend the coverage achievable by a single transmitter.
When the system has a priori knowledge of a pager's location, overall system utilization can increase as well. The system may use information describing the pager's location to route a page to only the transmitter that covers the position indicated by the location information. Only this transmitter broadcasts the page. The information transmission capacity of the other transmitters in the system is not consumed in broadcasting the page. Thus, overall system capacity utilization is improved.
However, a need exists for improved techniques in acquiring a priori knowledge of a pager's location. In one system, when a user roams between diverse areas of coverage the user has a duty to place a local phone call to a local page destination controller whenever the user arrives in a new area. During this phone call, the user identifies himself or herself as being in the area served by the local destination controller to which the phone call is made. Later, this destination controller contacts another controller which is associated with the origination of pages to the user and informs this origination controller of the identities of the subject pager and of the destination controller. Pages may thereafter be routed from the origination controller through land lines to the destination controller and broadcast from a transmitter associated with the destination controller.
Unfortunately, the local phone number of the destination controller to which the call must be placed is not a number that the user would readily know. Moreover, when the user roams between numerous local areas, the user is required to have phone numbers for all these numerous local areas. Furthermore, the user may not know when he or she has traveled out of a particular area of coverage. Accordingly, such a system is far too complicated for users to successfully operate when more than a few diverse areas of coverage are encompassed by the system.